RPC(3)                                                               Linux Programmer's Manual                                                               RPC(3)



NAME
       rpc - library routines for remote procedure calls

SYNOPSIS AND DESCRIPTION
       These  routines allow C programs to make procedure calls on other machines across the network.  First, the client calls a procedure to send a data packet to
       the server.  Upon receipt of the packet, the server calls a dispatch routine to perform the requested service, and then sends back a  reply.   Finally,  the
       procedure call returns to the client.

       To take use of these routines, include the header file <rpc/rpc.h>.

       The prototypes below make use of the following types:

           typedef int bool_t;

           typedef bool_t (*xdrproc_t) (XDR *, void *,...);

           typedef bool_t (*resultproc_t) (caddr_t resp,
                                           struct sockaddr_in *raddr);

       See the header files for the declarations of the AUTH, CLIENT, SVCXPRT, and XDR types.

       void auth_destroy(AUTH *auth);

              A  macro  that  destroys  the authentication information associated with auth.  Destruction usually involves deallocation of private data structures.
              The use of auth is undefined after calling auth_destroy().

       AUTH *authnone_create(void);

              Create and return an RPC authentication handle that passes nonusable authentication information with each remote procedure call.  This is the default
              authentication used by RPC.

       AUTH *authunix_create(char *host, int uid, int gid,
                             int len, int *aup_gids);

              Create  and return an RPC authentication handle that contains authentication information.  The parameter host is the name of the machine on which the
              information was created; uid is the user's user ID; gid is the user's current group ID; len and aup_gids refer to a counted array of groups to  which
              the user belongs.  It is easy to impersonate a user.

       AUTH *authunix_create_default(void);

              Calls authunix_create() with the appropriate parameters.

       int callrpc(char *host, unsigned long prognum,
                   unsigned long versnum, unsigned long procnum,
                   xdrproc_t inproc, char *in,
                   xdrproc_t outproc, char *out);

              Call  the  remote  procedure  associated with prognum, versnum, and procnum on the machine, host.  The parameter in is the address of the procedure's
              argument(s), and out is the address of where to place the result(s); inproc is used to encode the procedure's parameters,  and  outproc  is  used  to
              decode  the  procedure's results.  This routine returns zero if it succeeds, or the value of enum clnt_stat cast to an integer if it fails.  The rou‐
              tine clnt_perrno() is handy for translating failure statuses into messages.

              Warning: calling remote procedures with this routine uses UDP/IP as a transport; see clntudp_create() for restrictions.  You do not have  control  of
              timeouts or authentication using this routine.

       enum clnt_stat clnt_broadcast(unsigned long prognum,
                            unsigned long versnum, unsigned long procnum,
                            xdrproc_t inproc, char *in,
                            xdrproc_t outproc, char *out,
                            resultproc_t eachresult);

              Like  callrpc(),  except the call message is broadcast to all locally connected broadcast nets.  Each time it receives a response, this routine calls
              eachresult(), whose form is:

                  eachresult(char *out, struct sockaddr_in *addr);

              where out is the same as out passed to clnt_broadcast(), except that the remote procedure's output is decoded there; addr points to  the  address  of
              the machine that sent the results.  If eachresult() returns zero, clnt_broadcast() waits for more replies; otherwise it returns with appropriate sta‐
              tus.

              Warning: broadcast sockets are limited in size to the maximum transfer unit of the data link.  For ethernet, this value is 1500 bytes.

       enum clnt_stat clnt_call(CLIENT *clnt, unsigned long procnum,
                           xdrproc_t inproc, char *in,
                           xdrproc_t outproc, char *out,
                           struct timeval tout);

              A macro that calls the remote procedure procnum associated with the client handle, clnt, which is obtained with an RPC client creation  routine  such
              as  clnt_create().  The parameter in is the address of the procedure's argument(s), and out is the address of where to place the result(s); inproc is
              used to encode the procedure's parameters, and outproc is used to decode the procedure's results; tout is the time allowed for results to come back.

       clnt_destroy(CLIENT *clnt);

              A macro that destroys the client's RPC handle.  Destruction usually involves deallocation of private data structures, including clnt itself.  Use  of
              clnt  is  undefined  after  calling  clnt_destroy().   If the RPC library opened the associated socket, it will close it also.  Otherwise, the socket
              remains open.

       CLIENT *clnt_create(char *host, unsigned long prog,
                           unsigned long vers, char *proto);

              Generic client creation routine.  host identifies the name of the remote host where the server is located.  proto indicates which kind  of  transport
              protocol  to  use.  The currently supported values for this field are “udp” and “tcp”.  Default timeouts are set, but can be modified using clnt_con‐
              trol().

              Warning: Using UDP has its shortcomings.  Since UDP-based RPC messages can only hold up to 8 Kbytes of encoded data, this transport  cannot  be  used
              for procedures that take large arguments or return huge results.

       bool_t clnt_control(CLIENT *cl, int req, char *info);

              A  macro  used  to  change  or retrieve various information about a client object.  req indicates the type of operation, and info is a pointer to the
              information.  For both UDP and TCP, the supported values of req and their argument types and what they do are:

                  CLSET_TIMEOUT  struct timeval // set total timeout
                  CLGET_TIMEOUT  struct timeval // get total timeout

              Note: if you set the timeout using clnt_control(), the timeout parameter passed to clnt_call() will be ignored in all future calls.

                  CLGET_SERVER_ADDR  struct sockaddr_in  // get server's address

              The following operations are valid for UDP only:

                  CLSET_RETRY_TIMEOUT  struct timeval // set the retry timeout
                  CLGET_RETRY_TIMEOUT  struct timeval // get the retry timeout

              The retry timeout is the time that "UDP RPC" waits for the server to reply before retransmitting the request.

       clnt_freeres(CLIENT * clnt, xdrproc_t outproc, char *out);

              A macro that frees any data allocated by the RPC/XDR system when it decoded the results of an RPC call.  The parameter out  is  the  address  of  the
              results, and outproc is the XDR routine describing the results.  This routine returns one if the results were successfully freed, and zero otherwise.

       void clnt_geterr(CLIENT *clnt, struct rpc_err *errp);

              A macro that copies the error structure out of the client handle to the structure at address errp.

       void clnt_pcreateerror(char *s);

              Print a message to standard error indicating why a client RPC handle could not be created.  The message is prepended with string s and a colon.  Used
              when a clnt_create(), clntraw_create(), clnttcp_create(), or clntudp_create() call fails.

       void clnt_perrno(enum clnt_stat stat);

              Print a message to standard error corresponding to the condition indicated by stat.  Used after callrpc().

       clnt_perror(CLIENT *clnt, char *s);

              Print a message to standard error indicating why an RPC call failed; clnt is the handle used to do the call.  The message is prepended with string  s
              and a colon.  Used after clnt_call().

       char *clnt_spcreateerror(char *s);

              Like clnt_pcreateerror(), except that it returns a string instead of printing to the standard error.

              Bugs: returns pointer to static data that is overwritten on each call.

       char *clnt_sperrno(enum clnt_stat stat);

              Take  the same arguments as clnt_perrno(), but instead of sending a message to the standard error indicating why an RPC call failed, return a pointer
              to a string which contains the message.  The string ends with a NEWLINE.

              clnt_sperrno() is used instead of clnt_perrno() if the program does not have a standard error (as a program running as a  server  quite  likely  does
              not),  or  if the programmer does not want the message to be output with printf(3), or if a message format different than that supported by clnt_per‐
              rno() is to be used.  Note: unlike clnt_sperror() and clnt_spcreaterror(), clnt_sperrno() returns pointer to static data, but the result will not get
              overwritten on each call.

       char *clnt_sperror(CLIENT *rpch, char *s);

              Like clnt_perror(), except that (like clnt_sperrno()) it returns a string instead of printing to standard error.

              Bugs: returns pointer to static data that is overwritten on each call.

       CLIENT *clntraw_create(unsigned long prognum, unsigned long versnum);

              This  routine  creates a toy RPC client for the remote program prognum, version versnum.  The transport used to pass messages to the service is actu‐
              ally a buffer within the process's address space, so the corresponding RPC server should live in the same address space; see  svcraw_create().   This
              allows  simulation  of RPC and acquisition of RPC overheads, such as round trip times, without any kernel interference.  This routine returns NULL if
              it fails.

       CLIENT *clnttcp_create(struct sockaddr_in *addr,
                       unsigned long prognum, unsigned long versnum,
                       int *sockp, unsigned int sendsz, unsigned int recvsz);

              This routine creates an RPC client for the remote program prognum, version versnum; the client uses TCP/IP as a transport.   The  remote  program  is
              located  at Internet address *addr.  If addr->sin_port is zero, then it is set to the actual port that the remote program is listening on (the remote
              portmap service is consulted for this information).  The parameter sockp is a socket; if it is RPC_ANYSOCK, then this routine opens  a  new  one  and
              sets  sockp.   Since  TCP-based  RPC  uses buffered I/O, the user may specify the size of the send and receive buffers with the parameters sendsz and
              recvsz; values of zero choose suitable defaults.  This routine returns NULL if it fails.

       CLIENT *clntudp_create(struct sockaddr_in *addr,
                       unsigned long prognum, unsigned long versnum,
                       struct timeval wait, int *sockp);

              This routine creates an RPC client for the remote program prognum, version versnum; the client uses use UDP/IP as a transport.  The remote program is
              located  at  Internet  address  addr.   If  addr->sin_port is zero, then it is set to actual port that the remote program is listening on (the remote
              portmap service is consulted for this information).  The parameter sockp is a socket; if it is RPC_ANYSOCK, then this routine opens  a  new  one  and
              sets  sockp.   The  UDP  transport  resends the call message in intervals of wait time until a response is received or until the call times out.  The
              total time for the call to time out is specified by clnt_call().

              Warning: since UDP-based RPC messages can only hold up to 8 Kbytes of encoded data, this transport cannot be used  for  procedures  that  take  large
              arguments or return huge results.

       CLIENT *clntudp_bufcreate(struct sockaddr_in *addr,
                   unsigned long prognum, unsigned long versnum,
                   struct timeval wait, int *sockp,
                   unsigned int sendsize, unsigned int recosize);

              This  routine  creates  an  RPC  client for the remote program prognum, on versnum; the client uses use UDP/IP as a transport.  The remote program is
              located at Internet address addr.  If addr->sin_port is zero, then it is set to actual port that the remote  program  is  listening  on  (the  remote
              portmap  service  is  consulted  for this information).  The parameter sockp is a socket; if it is RPC_ANYSOCK, then this routine opens a new one and
              sets sockp.  The UDP transport resends the call message in intervals of wait time until a response is received or until  the  call  times  out.   The
              total time for the call to time out is specified by clnt_call().

              This allows the user to specify the maximum packet size for sending and receiving UDP-based RPC messages.

       void get_myaddress(struct sockaddr_in *addr);

              Stuff  the  machine's  IP  address  into  *addr, without consulting the library routines that deal with /etc/hosts.  The port number is always set to
              htons(PMAPPORT).

       struct pmaplist *pmap_getmaps(struct sockaddr_in *addr);

              A user interface to the portmap service, which returns a list of the current RPC program-to-port mappings on the host located at  IP  address  *addr.
              This routine can return NULL.  The command rpcinfo -p uses this routine.

       unsigned short pmap_getport(struct sockaddr_in *addr,
                           unsigned long prognum, unsigned long versnum,
                           unsigned int protocol);

              A  user  interface  to the portmap service, which returns the port number on which waits a service that supports program number prognum, version ver‐
              snum, and speaks the transport protocol associated with protocol.  The value of protocol is most likely IPPROTO_UDP or IPPROTO_TCP.  A  return  value
              of  zero  means  that the mapping does not exist or that the RPC system failed to contact the remote portmap service.  In the latter case, the global
              variable rpc_createerr contains the RPC status.

       enum clnt_stat pmap_rmtcall(struct sockaddr_in *addr,
                           unsigned long prognum, unsigned long versnum,
                           unsigned long procnum,
                           xdrproc_t inproc, char *in,
                           xdrproc_t outproc, char *out,
                           struct timeval tout, unsigned long *portp);

              A user interface to the portmap service, which instructs portmap on the host at IP address *addr to make an RPC call on your behalf to a procedure on
              that  host.   The  parameter *portp will be modified to the program's port number if the procedure succeeds.  The definitions of other parameters are
              discussed in callrpc() and clnt_call().  This procedure should be used for a “ping” and nothing else.  See also clnt_broadcast().

       bool_t pmap_set(unsigned long prognum, unsigned long versnum,
                       unsigned int protocol, unsigned short port);

              A user interface to the portmap service, which establishes a mapping between the triple [prognum,versnum,protocol] and port on the machine's  portmap
              service.   The  value of protocol is most likely IPPROTO_UDP or IPPROTO_TCP.  This routine returns one if it succeeds, zero otherwise.  Automatically
              done by svc_register().

       bool_t pmap_unset(unsigned long prognum, unsigned long versnum);

              A user interface to the portmap service, which destroys all mapping between the triple [prognum,versnum,*] and ports on the  machine's  portmap  ser‐
              vice.  This routine returns one if it succeeds, zero otherwise.

       int registerrpc(unsigned long prognum, unsigned long versnum,
                       unsigned long procnum, char *(*procname)(char *),
                       xdrproc_t inproc, xdrproc_t outproc);

              Register procedure procname with the RPC service package.  If a request arrives for program prognum, version versnum, and procedure procnum, procname
              is called with a pointer to its parameter(s); progname should return a pointer to its static result(s); inproc is used to decode the parameters while
              outproc is used to encode the results.  This routine returns zero if the registration succeeded, -1 otherwise.

              Warning: remote procedures registered in this form are accessed using the UDP/IP transport; see svcudp_create() for restrictions.

       struct rpc_createerr rpc_createerr;

              A global variable whose value is set by any RPC client creation routine that does not succeed.  Use the routine clnt_pcreateerror() to print the rea‐
              son why.

       void svc_destroy(SVCXPRT *xprt);

              A macro that destroys the RPC service transport handle, xprt.  Destruction usually involves deallocation of private data structures,  including  xprt
              itself.  Use of xprt is undefined after calling this routine.

       fd_set svc_fdset;

              A  global variable reflecting the RPC service side's read file descriptor bit mask; it is suitable as a parameter to the select(2) system call.  This
              is only of interest if a service implementor does not call svc_run(), but rather does his own asynchronous event processing.  This variable is  read-
              only (do not pass its address to select(2)!), yet it may change after calls to svc_getreqset() or any creation routines.

       int svc_fds;

              Similar to svc_fdset, but limited to 32 descriptors.  This interface is obsoleted by svc_fdset.

       svc_freeargs(SVCXPRT *xprt, xdrproc_t inproc, char *in);

              A  macro  that frees any data allocated by the RPC/XDR system when it decoded the arguments to a service procedure using svc_getargs().  This routine
              returns 1 if the results were successfully freed, and zero otherwise.

       svc_getargs(SVCXPRT *xprt, xdrproc_t inproc, char *in);

              A macro that decodes the arguments of an RPC request associated with the RPC service transport handle, xprt.  The parameter in is the  address  where
              the arguments will be placed; inproc is the XDR routine used to decode the arguments.  This routine returns one if decoding succeeds, and zero other‐
              wise.

       struct sockaddr_in *svc_getcaller(SVCXPRT *xprt);

              The approved way of getting the network address of the caller of a procedure associated with the RPC service transport handle, xprt.

       void svc_getreqset(fd_set *rdfds);

              This routine is only of interest if a service implementor does not call svc_run(), but instead implements custom asynchronous event  processing.   It
              is  called  when  the  select(2)  system  call has determined that an RPC request has arrived on some RPC socket(s); rdfds is the resultant read file
              descriptor bit mask.  The routine returns when all sockets associated with the value of rdfds have been serviced.

       void svc_getreq(int rdfds);

              Similar to svc_getreqset(), but limited to 32 descriptors.  This interface is obsoleted by svc_getreqset().

       bool_t svc_register(SVCXPRT *xprt, unsigned long prognum,
                           unsigned long versnum,
                           void (*dispatch)(svc_req *, SVCXPRT *),
                           unsigned long protocol);

              Associates prognum and versnum with the service dispatch procedure, dispatch.  If protocol is zero, the service is not registered  with  the  portmap
              service.  If protocol is nonzero, then a mapping of the triple [prognum,versnum,protocol] to xprt->xp_port is established with the local portmap ser‐
              vice (generally protocol is zero, IPPROTO_UDP or IPPROTO_TCP).  The procedure dispatch has the following form:

                  dispatch(struct svc_req *request, SVCXPRT *xprt);

              The svc_register() routine returns one if it succeeds, and zero otherwise.

       void svc_run(void);

              This routine never returns.  It waits for RPC requests to arrive, and calls the appropriate service procedure using svc_getreq()  when  one  arrives.
              This procedure is usually waiting for a select(2) system call to return.

       bool_t svc_sendreply(SVCXPRT *xprt, xdrproc_t outproc, char *out);

              Called by an RPC service's dispatch routine to send the results of a remote procedure call.  The parameter xprt is the request's associated transport
              handle; outproc is the XDR routine which is used to encode the results; and out is the address of the results.  This routine returns one if  it  suc‐
              ceeds, zero otherwise.

       void svc_unregister(unsigned long prognum, unsigned long versnum);

              Remove all mapping of the double [prognum,versnum] to dispatch routines, and of the triple [prognum,versnum,*] to port number.

       void svcerr_auth(SVCXPRT *xprt, enum auth_stat why);

              Called by a service dispatch routine that refuses to perform a remote procedure call due to an authentication error.

       void svcerr_decode(SVCXPRT *xprt);

              Called by a service dispatch routine that cannot successfully decode its parameters.  See also svc_getargs().

       void svcerr_noproc(SVCXPRT *xprt);

              Called by a service dispatch routine that does not implement the procedure number that the caller requests.

       void svcerr_noprog(SVCXPRT *xprt);

              Called when the desired program is not registered with the RPC package.  Service implementors usually do not need this routine.

       void svcerr_progvers(SVCXPRT *xprt);

              Called when the desired version of a program is not registered with the RPC package.  Service implementors usually do not need this routine.

       void svcerr_systemerr(SVCXPRT *xprt);

              Called  by a service dispatch routine when it detects a system error not covered by any particular protocol.  For example, if a service can no longer
              allocate storage, it may call this routine.

       void svcerr_weakauth(SVCXPRT *xprt);

              Called by a service dispatch routine that refuses to perform a remote procedure call due to  insufficient  authentication  parameters.   The  routine
              calls svcerr_auth(xprt, AUTH_TOOWEAK).

       SVCXPRT *svcfd_create(int fd, unsigned int sendsize,
                             unsigned int recvsize);

              Create  a  service  on top of any open descriptor.  Typically, this descriptor is a connected socket for a stream protocol such as TCP.  sendsize and
              recvsize indicate sizes for the send and receive buffers.  If they are zero, a reasonable default is chosen.

       SVCXPRT *svcraw_create(void);

              This routine creates a toy RPC service transport, to which it returns a pointer.  The transport is really  a  buffer  within  the  process's  address
              space, so the corresponding RPC client should live in the same address space; see clntraw_create().  This routine allows simulation of RPC and acqui‐
              sition of RPC overheads (such as round trip times), without any kernel interference.  This routine returns NULL if it fails.

       SVCXPRT *svctcp_create(int sock, unsigned int send_buf_size,
                              unsigned int recv_buf_size);

              This routine creates a TCP/IP-based RPC service transport, to which it returns a pointer.  The transport is associated with the  socket  sock,  which
              may  be  RPC_ANYSOCK,  in which case a new socket is created.  If the socket is not bound to a local TCP port, then this routine binds it to an arbi‐
              trary port.  Upon completion, xprt->xp_sock is the transport's socket descriptor, and xprt->xp_port is the transport's  port  number.   This  routine
              returns NULL if it fails.  Since TCP-based RPC uses buffered I/O, users may specify the size of buffers; values of zero choose suitable defaults.

       SVCXPRT *svcudp_bufcreate(int sock, unsigned int sendsize,
                                 unsigned int recosize);

              This  routine  creates  a UDP/IP-based RPC service transport, to which it returns a pointer.  The transport is associated with the socket sock, which
              may be RPC_ANYSOCK, in which case a new socket is created.  If the socket is not bound to a local UDP port, then this routine binds it  to  an  arbi‐
              trary  port.   Upon  completion,  xprt->xp_sock is the transport's socket descriptor, and xprt->xp_port is the transport's port number.  This routine
              returns NULL if it fails.

              This allows the user to specify the maximum packet size for sending and receiving UDP-based RPC messages.

       SVCXPRT *svcudp_create(int sock);

              This call is equivalent to svcudp_bufcreate(sock,SZ,SZ) for some default size SZ.

       bool_t xdr_accepted_reply(XDR *xdrs, struct accepted_reply *ar);

              Used for encoding RPC reply messages.  This routine is useful for users who wish to generate RPC-style messages without using the RPC package.

       bool_t xdr_authunix_parms(XDR *xdrs, struct authunix_parms *aupp);

              Used for describing UNIX credentials.  This routine is useful for users who wish to generate these credentials without using the  RPC  authentication
              package.

       void xdr_callhdr(XDR *xdrs, struct rpc_msg *chdr);

              Used  for  describing RPC call header messages.  This routine is useful for users who wish to generate RPC-style messages without using the RPC pack‐
              age.

       bool_t xdr_callmsg(XDR *xdrs, struct rpc_msg *cmsg);

              Used for describing RPC call messages.  This routine is useful for users who wish to generate RPC-style messages without using the RPC package.

       bool_t xdr_opaque_auth(XDR *xdrs, struct opaque_auth *ap);

              Used for describing RPC authentication information messages.  This routine is useful for users who wish to generate RPC-style messages without  using
              the RPC package.

       bool_t xdr_pmap(XDR *xdrs, struct pmap *regs);

              Used  for  describing  parameters  to various portmap procedures, externally.  This routine is useful for users who wish to generate these parameters
              without using the pmap interface.

       bool_t xdr_pmaplist(XDR *xdrs, struct pmaplist **rp);

              Used for describing a list of port mappings, externally.  This routine is useful for users who wish to generate these parameters  without  using  the
              pmap interface.

       bool_t xdr_rejected_reply(XDR *xdrs, struct rejected_reply *rr);

              Used for describing RPC reply messages.  This routine is useful for users who wish to generate RPC-style messages without using the RPC package.

       bool_t xdr_replymsg(XDR *xdrs, struct rpc_msg *rmsg);

              Used for describing RPC reply messages.  This routine is useful for users who wish to generate RPC style messages without using the RPC package.

       void xprt_register(SVCXPRT *xprt);

              After  RPC  service  transport  handles  are created, they should register themselves with the RPC service package.  This routine modifies the global
              variable svc_fds.  Service implementors usually do not need this routine.

       void xprt_unregister(SVCXPRT *xprt);

              Before an RPC service transport handle is destroyed, it should unregister itself with the RPC service package.   This  routine  modifies  the  global
              variable svc_fds.  Service implementors usually do not need this routine.

SEE ALSO
       xdr(3)
       The following manuals:
              Remote Procedure Calls: Protocol Specification
              Remote Procedure Call Programming Guide
              rpcgen Programming Guide
       RPC: Remote Procedure Call Protocol Specification, RFC 1050, Sun Microsystems, Inc., USC-ISI.

COLOPHON
       This  page  is  part  of  release  3.35 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can be found at
       http://man7.org/linux/man-pages/.



                                                                             2008-07-17                                                                      RPC(3)
